Fitting for formation of a fluid-conducting connection

ABSTRACT

1. Fitting for formation of a fluid-conducting connection 
     2. A fitting for formation of a fluid-conducting connection on a container ( 1 ) of plastic, in particular a tank for receiving a fluid, specifically a hydraulic fluid, having a connection part in the form of a hollow element ( 5 ) with a jacket ( 21 ) which extends along a longitudinal axis of the hollow element ( 5 ) between the ends ( 7, 23 ) thereof, which hollow element ( 5 ) is embedded in the plastic of the wall ( 3 ) of the container ( 1 ) so that an open end ( 7 ) of the hollow element ( 5 ) on the edge of an opening ( 9 ) in the container ( 1 ) and at least one partial area of the jacket ( 21 ) of the hollow element ( 5 ) are enclosed by the plastic of the wall ( 3 ) of the container ( 1 ).

The invention relates to a fitting for formation of a fluid-conducting connection on an opening in the wall of a container of plastic, in particular a tank for receiving a fluid, specifically a hydraulic fluid.

Plastic tanks are widely used in hydraulic systems to contain hydraulic fluids. Because of the possibility of relatively simple configuration, low weight, and corrosion resistance, plastic tanks are extensively used especially in hydraulic systems of machines such as excavators, wheel loaders, and the like.

Such tanks are usually produced by the well-known rotomolding or blow molding process, polyethylene or polyamide plastics, for example, being used for larger containers such as tanks for hydraulic fluids.

The advantages of corrosion resistance, low weight, and ease of molding are offset in the case of plastic tanks, however, by the disadvantage that production of fluid-conducting connections on openings in the plastic wall of the container or tank occasions certain difficulties. Because of the physical properties of the plastic material, the danger exists that deformations may occur in the area of the opening as a result of sealing forces and temperature effects, deformations which lead to leaking between plastic tanks and add-on elements even if costly sealing elements are employed.

On the basis of this state of the art the object of the invention is to make available a fitting which permits operationally reliable long-term, leak-free connection to an opening in a plastic container.

It is claimed for the invention that this object is attained by means of a fitting possessing the characteristics specified in claim 1 in its entirety.

The fitting claimed for the invention with the connection part in the form of a hollow element embedded in the plastic of the wall of a container accordingly makes available a reinforcing element which, because of the large area of embedding in the plastic material of the tank, which material not only encloses the hollow element at its open end at the opening in the container, but also extends over at least part of the area of the jacket of the hollow element, forms an intrinsically strong base for mounting add-on elements such as connections and/or sealing elements. The hollow material, preferably of metal, not only permits both operationally reliable joining with connections or add-on elements which are integrated into an associated hydraulic system but also contributes to reinforcement of the area of the plastic container or tank which is situated in the area of the opening.

In advantageous exemplary embodiments the hollow element for formation of a fluid-conducting connection has, spaced a certain distance from the ends of the hollow element, a connecting branch projecting from the jacket and extending transversely to the longitudinal axis, this connecting branch forming a fluid passage in the jacket of the hollow element, penetrating the wall of the container, and extending to the exterior.

If the hollow element, which preferably is configured to be integral with the connecting branch, is made of a metal material, the hollow element embedded over a large area reliably protects the plastic material of the container wall against deformation, since the loads applied to the hollow element such as fastening force, sealing force, and dynamic (vibration) and thermal effects cannot of themselves cause deformation of the structural hollow element, nor can these loads directly affect the plastic material of the container since they are introduced over the entire area of embedding of the hollow element in the container.

In advantageous exemplary embodiments the end of the connecting branch penetrating the wall of the container is configured to extend beyond the exterior of the wall of the container, the connecting branch being embedded in the plastic of the wall of the container in such a way that the projecting part of the connecting branch is enclosed at least partly in plastic. The embedding of hollow element and connecting branch over the entire area achieved in this manner guarantees particularly high structural strength.

In preferred exemplary embodiments the hollow element is configured as a circular cylinder and has, a short distance from the end associated with the opening in the container, a flange which is embedded in the plastic on the edge of the opening so that it is enclosed in its entirety externally by the portion of material extending along the jacket of the hollow element. Especially good anchoring of the hollow element against axial forces acting along the longitudinal axis of the hollow element is thereby achieved.

In exemplary embodiments in which the opening in the container may be sealed tightly by means of a sealing element in the form of a cap, for example, the hollow element may be embedded in such a way that its end projects outward beyond the edge of the opening in the container and so that a sealing configuration for a sealing connection with the closing element is provided on the projecting end.

As an alternative, the hollow element may have, in its interior in the vicinity of its opening associated with the opening in the container, an annular groove as the seat of an annular sealing element which acts together with an annular surface to effect sealing, this annular surface extending from a closing element which may be mounted on the opening into the interior of the hollow element.

In the case of a closing element in the form of a cap, the latter may also have an element on which is provided a sealing configuration projecting radially beyond the edge of the hollow element in order to effect sealing together with the wall enclosing the opening.

On its end facing away from the opening in the container the hollow element may have a seat for mounting a tank-top filter, one which is accessible by way of the opening in the container by way of the assumed closing element, for example, for the purpose of replacing the hollow element.

The invention will be described in greater detail below with the aid of the exemplary embodiments illustrated in the drawing, in which

FIG. 1 presents a vertical section exclusively of an upper partial area of a container in the form of a plastic tank which is provided for the purpose of receiving an hydraulic fluid and is provided with a fitting representing an exemplary embodiment of the invention and also forming a receptacle for a tank-top filter, and

FIG. 2 presents a vertical section corresponding to that in FIG. 1 of a second exemplary embodiment.

FIG. 1 shows the upper area of a container in the form of a plastic tank 1 which is made of a plastic material suitable for larger containers by the known rotomolding process (cf. Schaab/Stoeckhert, AKunststoff Maschinenführer@ [Plastic Machine Operator]), pages 561-564). In the rotomolding process a hollow element 5 in the form of a circular cylinder is molded in the plastic wall 3 so that upper end identified by 7 in the drawing of the hollow element 5 is adjacent to the interior of an opening 9 in the wall 3 of the tank 1. In the example shown in FIG. 1 the end 7 of the hollow element 5 projects slightly beyond the exterior of the wall 3, there being provided on the projecting end a sealing ring 11 which in conjunction with a closing element in the form of a screw cap 13 permits tight closing on the respective end 7 of the hollow element 5 and accordingly sealing of the opening 9 in the container wall 3.

The cap 13 has a threaded component in the form of an annular element 15 which may be screwed by means of an interior threading 17 onto the interior surface of the hollow element 5.

In the exemplary embodiment shown, the hollow element 5 is integrated by squeeze molding and has externally near its end 7 a circumferential flange 19. Approximately in the central area of its jacket 21, between the upper end 7 and lower end 23, there extends from the jacket 21 a connecting branch 25 integral with this jacket 21, at a right angle to the longitudinal or cylinder axis of the hollow element 5, the wall thickness of the branch 25 decreasing slightly from the jacket 21 to the free end 27, something which favors molding of the workpiece in production of the hollow element 5 by squeeze molding. On its lower end 23 the jacket 21 of the hollow element 5 has an end edge 29 projecting radially slightly inward which slightly reduces the diameter of the respective opening of the interior 31 of the hollow element 5 in the form of a circular cylinder and forms an annular shoulder 33 which forms a seat for a commercially available tank-top filter 37 which rests on the annular shoulder by way of a sealing ring 35. A pressure spring 39 mounted between the upper side of the filter 37 and the cap 13 holds the filter 37 against the seat by the force of the tension of the spring.

As is clearly to be seen in the drawing, the hollow element 5 is embedded in the plastic of the container wall 3 so that the hollow element 5 is enclosed in plastic at the upper end 7 of the plastic, over the entire exterior surface of the flange 19, and so that the plastic extends along the jacket 21 of the hollow element 5 to the lower end 23, where the plastic also extends beyond the lower end edge 29 of the jacket 21. In addition, not only is the connecting branch 25 enclosed entirely in plastic over the section between jacket 21 and the interior of the container wall 3, but the plastic of the wall 3 also encloses the connecting branch 25 on the exterior of the tank 1. As has already been mentioned, the hollow element 5 forms a connection part for add-on elements, such as a fluid connection on the end of the connecting branch 25, this connection part acting as a reinforcing element which, because of the large area of enclosure in the plastic material of the container wall 3, causes the forces acting on the latter to introduce such lower specific surface pressure into the plastic of the tank 1 that deformation of the tank is prevented.

The exemplary embodiment illustrated in FIG. 2 differs from that shown in FIG. 1 only to the extent that the sealing configuration between cap 13 and the upper end 7 of the hollow element 5 is different in shape. In the example shown in FIG. 2 the upper end 7 of the hollow element 5 is more or less flush with the exterior of the plastic wall 3 of the tank 1. In place of the sealing configuration 11, shown in the example in FIG. 1 to be provided as an axial seal between hollow element 5 and cap 13, in the example illustrated in FIG. 2 there is an annular groove in the vicinity of the end 7 on the interior surface of the hollow element 5, in which groove a radial seal 41 is seated. This seal 41 acts in conjunction with an annular surface 43 which is positioned on the annular element 15 of the cap 13. This annular element 15, which extends into the interior 31 of the hollow element 5, has, following its unthreaded annular surface 43, which acts in conjunction with the seal 41, a section with exterior threading 47 which may be screwed into the interior threading 17 of the hollow element 5.

In addition to the radial seal 41 a sealing connection is provided between cap 13 and container 1 by means of an axial seal 49 which is seated in an annular groove on the surface of a circumferential edge 51 facing the wall 3 of the cap 13. This circumferential edge 51 projects radially above the upper end 7 of the hollow element 5 a greater distance than does the circumferential edge 14 of the first exemplary embodiment. The axial seal 49 in the example shown in FIG. 2 accordingly acts directly in conjunction with the exterior of the wall 3 of the tank 1.

In the examples illustrated in the figures and described in the foregoing there is, on the end 7 of the hollow element 5 associated with the opening 9 in the container wall, a closing element in the form of a cap 13. The opening 9 in the wall 3 of the container 1 serves in these examples as access opening for the tank-top filter 37, while the connecting branch 25 connected to the interior 31 of the hollow element 5 is provided for formation of a fluid-conducting connection. It will be understood that connecting or add-on elements of a kind different from that of the cap 13 could be provided on the connection part in the form of the hollow element 5. For example, a connecting head of a tank-top filter could be fastened on the associated end 7 of the hollow element 5 in place of the cap 13. In each instance the advantages in question based on the presence of a connection part in the form of a hollow element 5 embedded over a large area into the plastic material of the wall 3 of the tank 1 are also obtained with such exemplary embodiments. 

1. A fitting for formation of a fluid-conducting connection on a container (1) of plastic, in particular a tank for receiving a fluid, specifically a hydraulic fluid, having a connection part in the form of a hollow element (5) with a jacket (21) which extends along a longitudinal axis of the hollow element (5) between the ends (7, 23) thereof, which hollow element (5) is embedded in the plastic of the wall (3) of the container (1) so that an open end (7) of the hollow element (5) on the edge of an opening (9) in the container (1) and at least one partial area of the jacket (21) of the hollow element (5) are enclosed by the plastic of the wall (3) of the container (1).
 2. The fitting as claimed in claim 1, wherein the hollow element (5) has, at a distance from the ends (7, 23) of such hollow element (5), a connecting branch (25) which, extending transversely to the longitudinal axis from the jacket (21), such connecting branch (25) forming a fluid passage in the jacket (21) of the hollow element (5) and, extending to the exterior, penetrates the wall (3) of the container (1).
 3. The fitting as claimed in claim 2, wherein the hollow element (5) is configured to be integral with the connecting branch (25) and consists of a metal material.
 4. The fitting as claimed in claim 2, wherein the end (27) of the connecting branch (25) penetrating the wall (3) of the container (1) is configured to project outward beyond the exterior of the wall (3) of the container (1) and is embedded in the plastic of the wall (3) of the container (1) so that the projecting part of the connecting branch (25) is at least partly enclosed by plastic.
 5. The fitting as claimed in claim 4, wherein the part of the connecting branch (25) extending from the inside of the wall (3) of the container (1) to the jacket (21) of the hollow element (5) is enclosed over its entire area by plastic, so that an uninterrupted plastic structure extends from the portion of material enclosing the jacket (21) of the hollow element (5) along the connecting branch (25) to the wall (3) of the container (1) and beyond the exterior of the container (1) along the projecting part of the connecting branch (25).
 6. The fitting as claimed in claims 1, wherein the hollow element (5) is in the form of a circular cylinder and has, a short distance from the end (7) associated with the opening (9) in the container (1), a flange (19) which is embedded in the plastic on the edge of the opening (9) so that it is fully enclosed on the exterior by the portion of plastic material extending along the jacket (21) of the hollow element (5).
 7. The fitting as claimed in claim 6, wherein the hollow element (5) is so embedded that its end (7) projects outward beyond the edge of the opening (9) in the container (1) and wherein the projecting end (7) has a sealing configuration (11) for a sealing connection with a closing element (13) which may be positioned on the opening (9) in the container (1) in order to effect closing.
 8. The fitting as claimed in claim 6, wherein the hollow element (5) has, in its inner surface, in the vicinity of its end (7) associated with the opening (9) in the container (1), an annular groove as seat for an annular sealing element (41), an annular groove which acts in conjunction with an annular surface (43) in order to effect sealing, such surface (43) extending from a closing element (13) which may be mounted on the opening (9) into the interior of the hollow element (5).
 9. The fitting as claimed in claim 7, wherein there is provided as closing element a cap (13) with a threaded element (47) provided with exterior threading, such element (47) being in the form of an annular element (15) which may be screwed into an interior threading (17) on the interior surface of the hollow element (5).
 10. The fitting as claimed in claims 8, wherein the annular element (15) forms, by way of an unthreaded section, the annular surface (43) which works in conjunction with the annular sealing element (41) on the interior surface of the hollow element (5).
 11. The fitting as claimed in claim 9, wherein the cap (13) has a radially extending circumferential edge (14; 51) which overlaps an edge of the hollow element (5).
 12. The fitting as claimed in claims 7, wherein there is provided on the circumferential edge (14) a sealing surface to work in conjunction with the sealing configuration (11) on the projecting end (7) of the hollow element (5).
 13. The fitting as claimed in claim 11, wherein the circumferential edge (51) of the cap (3) has a part projecting radially beyond the edge of the hollow element (5) and wherein there is provided on this part projecting radially a sealing configuration (49) for formation of a seal with the wall (3) of the container (1) enclosing the opening (9).
 14. The fitting as claimed in claim 1, wherein the hollow element (5) has, on its end (23) facing away from the opening (9), a seat (33) for seating a tank-top filter (37). 